The back-to-school shopping season is already off to a fast start for Amazon.com Inc.

Amazon, No. 1 in the 2017 Internet Retailer Top 500, has grown its sales of school supplies by 35% year over year during the first two weeks of the back-to-school shopping season, according to estimates from One Click Retail. The online retail analytics provider bases its estimate on what it calls “a combination of website indexing, machine learning and proprietary software.” Amazon declined to comment.

Amazon is showing particularly strong growth in sales of youth apparel and tablet devices, which are up by 61% and 98% respectively compared to last year, One Click Retail says.

“While this early indication doesn’t necessarily predict the more sales-heavy remainder of ‘Back-to-School’ season, it does show early velocity,” writes One Click Retail managing partner Spencer Millerberg, a former Amazon employee. “It paints a picture that more parents are multi-tasking on Amazon during ‘back-to-school night’ for those supplies versus stopping by the store on the way home.”

Last month, the National Retail Federation estimated that U.S. shoppers would spend $83.6 billion this year on back-to-school and back-to-college products, up 10.3% from $75.8 billion last year. The NRF reports that 45.5% of all back-to-school shoppers are planning on buying online this year, while 44.1% of back-to-college shoppers are planning on buying online.

Meanwhile, two surveys—each of the same 8,802 U.S. households—conducted by brand research consultancy Brand Keys from mid-June through mid-August show that shoppers plan to spend an average of $716 on back-to-school products this year, up 6.1% from $675 last year. In both surveys, shoppers named Amazon and Wal-Mart Stores Inc. (No. 3),in that order, as their primary retailers for school-related supplies.

“While the past few years have proved this finding, this year’s back-to-school marketplace further confirms that Amazon.com has become consumers’ default shopping platform—early or late in the season,” says Robert Passikoff, founder and president of Brand Keys.

Early back-to-school shopping focuses mostly on such supplies as notebooks, pens and pencils, computers and calculators, and such products account for 41% of this year’s anticipated average spend, according to Brand Keys. The second wave of spending is expected to occur in late August and “59% of 2017’s average anticipated spend has been predominantly budgeted for clothing, shoes (athletic and dress), books and study aids,” Passikoff says.

Online travel accessories retailer eBags Inc. (No. 155) hopes to reach back-to-school shoppers by partnering with YouTube personalities and bloggers to feature its products, with a focus on backpacks. In announcing the move, eBags says the nine social media influencers it is working with, who are high school are college students, have a combined audience of more than 20 million people.

“With YouTube being the world’s second-largest search engine, we understand how important it is to reach our customers where they live—online,” eBags CEO Mike Edwards says.